Cassini finds hints of activity at Saturn moon Dione

May 30, 2013

The Cassini spacecraft looks down, almost directly at the north pole of Dione. The feature just left of the terminator at bottom is Janiculum Dorsa, a long, roughly north-south trending ridge. Image credit: NASA/JPL/Space Science Institute

(Phys.org) —From a distance, most of the Saturnian moon Dione resembles a bland cueball. Thanks to close-up images of a 500-mile-long (800-kilometer-long) mountain on the moon from NASA's Cassini spacecraft, scientists have found more evidence for the idea that Dione was likely active in the past. It could still be active now.

"A picture is emerging that suggests Dione could be a fossil of the wondrous activity Cassini discovered spraying from Saturn's geyser moon Enceladus or perhaps a weaker copycat Enceladus," said Bonnie Buratti of NASA's Jet Propulsion Laboratory in Pasadena, Calif., who leads the Cassini science team that studies icy satellites. "There may turn out to be many more active worlds with water out there than we previously thought."

Other bodies in the solar system thought to have a subsurface ocean - including Saturn's moons Enceladus and Titan and Jupiter's moon Europa - are among the most geologically active worlds in our solar system. They have been intriguing targets for geologists and scientists looking for the building blocks of life elsewhere in the solar system. The presence of a subsurface ocean at Dione would boost the astrobiological potential of this once-boring iceball.

Hints of Dione's activity have recently come from Cassini, which has been exploring the Saturn system since 2004. The spacecraft's magnetometer has detected a faint particle stream coming from the moon, and images showed evidence for a possible liquid or slushy layer under its rock-hard ice crust. Other Cassini images have also revealed ancient, inactive fractures at Dione similar to those seen at Enceladus that currently spray water ice and organic particles.

The mountain examined in the latest paper—published in March in the journal Icarus—is called Janiculum Dorsa and ranges in height from about 0.6 to 1.2 miles (1 to 2 kilometers). The moon's crust appears to pucker under this mountain as much as about 0.3 mile (0.5 kilometer).

This image, which is composed of data obtained by NASA's Cassini spacecraft, shows the topography of a mountain known as Janiculum Dorsa on the Saturnian moon Dione. Color denotes elevation, with red as the highest area and blue as the lowest. Image credit: NASA/JPL-Caltech/SSI/Brown

"The bending of the crust under Janiculum Dorsa suggests the icy crust was warm, and the best way to get that heat is if Dione had a subsurface ocean when the ridge formed," said Noah Hammond, the paper's lead author, who is based at Brown University, Providence, R.I.

Dione gets heated up by being stretched and squeezed as it gets closer to and farther from Saturn in its orbit. With an icy crust that can slide around independently of the moon's core, the gravitational pulls of Saturn get exaggerated and create 10 times more heat, Hammond explained. Other possible explanations, such as a local hotspot or a wild orbit, seemed unlikely.

Scientists are still trying to figure out why Enceladus became so active while Dione just seems to have sputtered along. Perhaps the tidal forces were stronger on Enceladus, or maybe the larger fraction of rock in the core of Enceladus provided more radioactive heating from heavy elements. In any case, liquid subsurface oceans seem to be common on these once-boring icy satellites, fueling the hope that other icy worlds soon to be explored - like the dwarf planets Ceres and Pluto - could have oceans underneath their crusts. NASA's Dawn and New Horizons missions reach those dwarf planets in 2015.

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User comments : 8

Ah ha, more evidence of electric currents, but astrophysicists prefer ad hoc explanations to real laboratory testable theories. Mind games and theoretical fantasies are much more fun for them than the idea that those "faint particle streams" are in fact electric currents and those electric currents actually do something.

Well, once you really understand the morphology and behavior of those "geysers" it becomes remarkably plain to see that the idea behind subsurface oceans being squeezed out of the planet are complete nonsense.

There is also the anomalous heating that occurs at the "tiger stripes" (predicted by Wal Thornhill of the EUT) of the south polar region. A totally unexpected result by NASA;

"This is as astonishing as if we'd flown past Earth and found that Antarctica was warmer than the Sahara," said John Spencer, an astronomer from the Southwest Research Institute and a co-investigator of the Cassini mission".

The decision to ignore the electrical machining argument is born entirely from the larger, relic philosophy of the universe as a mechanistic system -- the subject of Rupert Sheldrake's numerous "Science Set Free" talks and book by the same title, as well as the decades-long line of investigation published in IEEE's Transactions on Plasma Science and discussed in the numerous Electric Universe books and Thunderbolts Picture of the Days.

Those who imagine that this controversy can be decided by simply ignoring it are apparently not the fans of the scientific method that they may claim to be. Ostracism and dismissals of arguments, determined entirely upon the worldview rather than an investigation into the evidence & claims, are features of human psychology and sociology.

What has clearly been missed by many conventional thinkers is the role that limitations to observations & experimentation play in creating verisimilitude for BOTH of these paradigms.

Should we really be surprised that the mechanistic interpretation will be favored first, before the later realization that electricity & magnetism are playing bigger roles than imagined? No, this would naturally follow from the larger historical context of where science came from: Humans must struggle to see all of the numerous forms which E&M can take. The conventional worldview clings to the optical realm as if it remains the core basis for what we see in the universe today, even though much of our knowledge of the universe now relies very heavily upon the much larger electromagnetic bandwidth; even though we now know that most of what we see in space with telescopes is matter in the plasma state; and even though we can observe that magnetic fields are actually quite common.

Should we abandon our knowledge that magnetic fields tend to go hand-in-hand with electric currents, in order to save our mechanistic worldview?

Yep and my individual conclusion is, that the Plasma universe guys are dull crackpots, who are mechanically pushing homological models to unrelated phenomena, just because the gravitomagnetic and Maxwell equations are homomorphic, i.e. they're describing unrelated phenomena at different scales similarly. In addition, the Plasma universe here is OT here.